<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>回顾一个DOM操作</title>
</head>
<style>
    .demo{
        background-color: orange;
    }
</style>
<body>

    <button id="btn">点我创建一个输入框</button>

    <script type="text/javascript">
        const btn = document.getElementById('btn');
        btn.onclick = ()=>{
            const input = document.createElement('input');

            input.className = 'demo';
            input.value = 99;
            input.onclick = ()=>{alert(1)}

            document.body.appendChild(input)

            // 这里得放在页面中已经有input框之后才能生效
            input.focus();
            console.log(input.parentElement);
        }

    </script>

    
</body>
</html>